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RD-861
Credit - © Dietrich Haeseler
Engine Model: RD-861. Manufacturer Name: RD-861. Government Designation: 11D25. Other Designations: S5.23, D-25. Designer: Yuzhnoye. Developed in: 1968-72. Application: Tsyklon 2 and 3 stage 3; Ikar. Propellants: N2O4/UDMH. Thrust(vac): 78.710 kN (17,695 lbf). Isp: 317 sec. Burn time: 130 sec. Mass Engine: 123 kg (271 lb). Diameter: 1.53 m (5.01 ft). Length: 1.56 m (5.11 ft). Chambers: 1 + 4 + 2. Chamber Pressure: 88.80 bar. Area Ratio: 112.40. Oxidizer to Fuel Ratio: 2.10. Thrust to Weight Ratio: 65.25. Country: Ukraine. Status: In production. First Flight: 1965. Last Flight: 2006. Flown: 229.

Based on RD-854. Thrust vector control by 4 nozzles (thrust 98 N each) fed from a gas generator. Mass given in ref. IAF-97-S.1.04 is 162 kg instead of 123 kg originally stated.

Engine Model: RD-861G. Manufacturer Name: RD-861G. Government Designation: 11D25G. Designer: Yuzhnoye, Fiat Avio. Developed in: 1996-. Application: Vega upper stage. Propellants: N2O4/UDMH. Thrust(vac): 76.453 kN (17,187 lbf). Isp: 325 sec. Burn time: 400 sec. Mass Engine: 185 kg (407 lb). Length: 1.66 m (5.46 ft). Chambers: 1 + 4. Chamber Pressure: 88.80 bar. Area Ratio: 112.40. Oxidizer to Fuel Ratio: 2.41. Thrust to Weight Ratio: 42.14. Country: Ukraine + Italy. Status: Developed 1996-.

Proposed uprate of RD-861 engine. Thrust vector control by gimbal, roll control by 4 nozzles (thrust 29 N each) and new arrangement of turbine exhaust lines for improved performance.

Engine Model: RD-861K. Manufacturer Name: RD-861K. Designer: Yuzhnoye. Developed in: 2003. Application: Tsyklon 2 and 3 stage 3; Ikar. Propellants: N2O4/UDMH. Thrust(vac): 77.630 kN (17,452 lbf). Isp: 330 sec. Burn time: 370 sec. Mass Engine: 194 kg (427 lb). Diameter: 1.53 m (5.01 ft). Length: 1.56 m (5.11 ft). Chambers: 1. Oxidizer to Fuel Ratio: 2.41. Country: Ukraine. Status: Developed 2005.

An improved version of the RD-861 engine first described in a 2005 brochure. High pressure fuel was used to gimbal the engine in two planes, replacing the four thrust vector engines of earlier models. Mass of the engine increased, but specific impulse was increased by 15.6 s; the number of restarts in flight was increased to three; and the burn time was tripled. The mixture ratio was controlled with an accuracy of ±1.0%.

RD-861 used on Rocket Stages
Bibliography:

  • Isakowitz, Steven J,, International Reference to Space Launch Systems Second Edition, AIAA, Washington DC, 1991 (succeeded by 2000 edition).
  • Shnyakin, Klimov, Shulga, IAF-Congress Turin, 1997, "Uprated Main Liquid Propellant Rocket Engine For CYCLONE LV Third Stage", IAF-97-S.1.04 via Dietrich Haeseler.
  • Shnyakin, V N, Shidkostnye Raketye Dvigateli - Opisanie i Osnovnye Tekhnicheskie Dannye, GKB Yuzhnoe "Yangel", Dnepropetrovsk 1996 via Dietrich Haeseler.
  • Yuzhnoye Company Web Site, Web Address when accessed: http://www.yuzhnoye.com/.
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